1. Field of the Invention
The present invention relates to a flame-retardant hardener for epoxy resin and a flame-retardant resin material comprising the same, which can be applied to fields of printed circuit board material or integrated circuit (IC) packaging material, etc.
2. Description of the Prior Arts
When resins are used as a printed circuit board material and an IC packaging material, the monomer of resins are typically brominated before preparing a brominated resin in order to make the products with flame-retardant characteristics. Although the printed circuit board material and IC packaging material made of brominated resins usually have good flame-retardant characteristics, the brominated resins produce high corrosive bromine free radicals, hydrogen bromide (HBr), high toxic polybromine dibenzofurans and polybromine dibenzodioxins when being incinerated. The aforementioned substances cause a huge damage to both people and the environment.
In order to overcome the problems, a phosphorus-containing group contained in 9,10-dihydro-9-oxa-10-phosphaphenanathrene-10-oxide (abbreviated as DOPO) is attached onto the epoxy resin to provide a flame-retardant resin material, which is able to replace the toxic brominated resin. When a product made of DOPO is heated at a high temperature, the phosphorus-containing group comprised in DOPO will produce non-volatile phosphorous compounds such as phosphoric acid (H3PO4) and Poly(phosphorous acid). Because poly(phosphorous acid) has an ability of protonating organic molecules and has a strong dewaterability, and because H3PO4 can be an agglutinant of carbon for forming an insulated layer and also has a strong dewaterability, the non-volatile phosphorous compounds can make a resin material have a desired flame-retardant characteristic.
Generally, resins for printed circuit board material and IC packaging material must be synthesized with a curing agent (hardener) and followed by other processes. Based on the aforementioned means of offering a flame-retardant characteristic to resins with DOPO, a halogen-free flame-retardant printed circuit board material and IC packaging material can be also obtained by DOPO-containing curing agent.
The aforementioned hypothesis that a curing agent attached with a phosphorus-containing group of DOPO will provide a flame-retardant material has been well known in the related arts. However, a feasible and specific process and technique still have not been developed. TW patent No. 593526, JP patent No. 3653247 and U.S. Pat. No. 6,797,821 disclose a compound represented by the

The compound (so-called DOPO-DICY) is obtained by attaching a phosphorus-containing group of DOPO onto a curing agent (dicyandiamide, DICY). According to the preparation method disclosed by the publications, DICY must be heated at 120° C. until completely melted. However, DICY has a high melting point about 209.5° C., it is difficult to use a conventional apparatus disclosed by the patents to perform a synthesis of DOPO-DICY. Moreover, there is still a need to develop other various curing agents for improving the technical development.